1. Field of the Invention
The present invention relates to a resin composition which provides a molded product in which the rate of an active compound having low vaporizability to be released from the molded product has been controlled and the utilization of the active compound contained therein been improved and further relates to the molded product obtained from the resin composition. More particularly, it relates to a resin composition which provides a molded product which stably retains therein the active compound under sealed condition and releases a suitable amount of the active compound under opened condition and, thus, is improved in utilization of the active compound and to the molded product obtained from the resin composition.
2. Description of the Related Prior Art
Resin compositions containing an active compound in the resin and molded products made from the compositions have, hitherto, been known and have been used in a wide variety of fields because molded products of various shapes can be relatively inexpensively obtained. According to these known art, the active compound is slowly released from the molded product by vaporization or oozing to the surface of the molded product, namely, so-called bleeding and the active compound exhibits its effect.
In the case of the active compound being low in vaporizability, the active compound is hardly released by vaporization, but is mainly released by bleeding. The bleeding occurs when the compound is retained in the molded product in an amount more than saturation dissolving amount (supersaturation amount) in the molded product and it is a phenomenon that the supersaturation portion (=amount of the added active compound--the saturation dissolution amount of the compound in the molded product) migrates to the surface of the molded product with lapse of time until the supersaturation portion reaches the surface. Therefore, in the case of a molded product obtained from a resin composition containing an active compound in an amount exceeding the saturation dissolution amount, the active compound bleeds to the surface of the molded product with lapse of time, but since the saturation dissolution amount of the active compound in the resin is fixed, it is generally difficult to control the bleeding rate or the starting time of bleeding of the active compound from the molded product. Furthermore, since the active compound in an amount less than the saturation dissolution amount can be relatively stably retained in the resin, substantially no active compound is released from the molded product after the supersaturation portion has bled.
Moreover, in the case of a molded product obtained from a resin composition containing an active compound in an amount more than the saturation dissolution amount, the active compound of the supersaturation portion is also released with time during storage and preservation of the molded product, which causes bleeding to the surface of the molded product or staining of the surface of other materials with which the molded product contacts during storage or preservation. This is not preferred. Further, if the active compound of the supersaturation portion is released during storage or preservation, the active compound sticks to the materials other than the targets (e.g., package of the molded products, hands of the person who equips the molded products at the starting of use) before the active compound develops its inherent effect, and, as a result, the period during which the molded product releases the active compound becomes shorter than desired or the active compound is no longer released from the molded product at the desired time. Thus, there is the possibility of causing reduction in the utilization of the active compound.
As a result of the intensive research, the inventors have found that a resin composition which comprises a resin containing an active compound and a vaporizable plasticizer gives a molded product which is controlled in the bleeding starting time and the bleeding rate of the active compound low in vaporizability. Thus, the present invention has been accomplished.